nervous system: neural tissue - mt. san antonio...
TRANSCRIPT
Overview
• Includes all neural 8ssue in the body
• 2 divisions 1. Central (CNS) 2. Peripheral (PNS)
– Afferent • Sensory • Info to CNS • Receptors
– Efferent • Motor • Info from CNS • Effectors
PNS Organiza8on
• Soma8c – Skeletal muscle – Soma8c motor
• CNS controls skeletal muscle – Soma8c sensory
• Sensory info from muscles to CNS
• Autonomic (Visceral) – Gut structures – Visceral motor
• Autonomic nervous system (ANS)
• Sympathe8c division • Parasympathe8c division
– Visceral sensory
Cellular Organiza8on
• 2 dis8nct types of cells 1. Neurons • Transfer and processing informa8on in the nervous system
2. Neuroglia • Cells that support and protect neurons
CNS Glial Cells
• Astrocytes – Inters88al environment – Blood‐brain barrier – Structural support – Repairing damaged nervous 8ssue – Neuron development
• Oligodendrocytes – Not all nerves in the CNS are myelinated – myelin
• Microglia – macrophage
• Ependymal cells – Cerebral spinal fluid (CSF)
PNS Glial Cells
• Schwann cells – Myelin
• All peripheral nerves are myelinated
– Nodes of Ranvier • Axolemma
– Neuron plasma membrane
• Neurilemma – Superficial cytoplasmic covering
• Satellite cells
Neural Development and Growth
• Stem cells differen8ate into neurons or glia (before birth)
• Each neuronal daughter cell differen8ates and sends out processes that will be axons and dendrites
• Growth cone – Forms a 8p at the end of an axon
– Directs the route and final target for the axon – Guided along glial cells – Synapses become ac8ve before matura8on
• Determines final func8on
• Apoptosis – Programmed cell death
– 50‐70% of neurons and synapses in developing CNS
Neural Regenera8on
• Severed neurons can be repaired as long as the damage – Occurs outside of the CNS
– Does not damage the soma
• Slow process – 1mm/day
Structural Classifica8on of Neurons
• Anaxonic neuron – CNS – Special sense organs
• Bipolar neuron – Single dendrite – Centrally located soma – Between axon and dendrite – Special senses (vision,
smell, hearing) – Not myelinated
• Pseudounipolar neuron – Con8nuous axon‐dendrite
processes – Soma is off to the side – Visceral sensory neurons – Axons may be myelinated
• Mul?polar neuron – Mul8ple dendrites – Single axon – Most common in CNS
• Soma8c motor neurons • All axons are myleninated
Func8onal Classifica8on of Neurons
• Sensory neurons – Afferent division of PNS – Deliver info to CNS – Pseudounipolar neurons
• Afferent fibers • From sensory receptors to spinal cord or brain
• Motor neurons
• Interneurons
Func8onal Classifica8on of Neurons Sensory Neurons
• Afferent division of PNS • Soma?c sensory neurons
– Deliver info to CNS • Outside world • Our posi8on in it
– Receptors located in the belly of muscles • Monitor tension • Monitor stretch
– Pseudounipolar neurons • Afferent fibers • From sensory receptors to spinal cord or brain
• Visceral sensory neurons – Transmit info on internal condi8ons – Status of organ systems
Func8onal Classifica8on of Neurons Sensory Neuron Receptors
• Types – Exteroreceptor (soma8c sensory receptors)
• External environment • Touch • Temperature • Pressure • Special senses (vision, hearing, olfac8on)
– Proprioceptor (soma8c sensory neurons) • Posi8on and movement of skeletal muscles and joints
– Interoreceptor (visceral sensory neurons) • Diges8ve, respiratory, cardiovascular, urinary, reproduc8ve systems • Sensa8ons of deep pressure • Pain • Taste
Func8onal Classifica8on of Neurons Motor Neurons
• Efferent division of PNS • Mul8polar neurons • S8mulates or modifies the ac8vity of – Peripheral 8ssue – Organ – Organ system
• Soma8c nervous system • Visceral nervous system (Autonomic nervous system)
Func8onal Classifica8on of Neurons Soma8c Nervous System
• Soma8c motor neurons
• Innervate skeletal muscles • Cell bodies within CNS • Axons extend to neuromuscular synapses • Most ac8vi8es are consciously controlled
Func8onal Classifica8on of Neurons Autonomic Nervous System
• Visceral motor neurons • 2 neuron system – Preganglionic fiber
• Soma in the brain or spinal cord • Control neurons in peripheral ganglia
– Postganglionic fiber • Soma in a peripheral ganglia • Control the peripheral effectors
– 2 divisions of the ANS • Sympathe8c
– “Fight or Flight” • Parasypathe8c
– “Rest and Repose”
Peripheral Effectors: Smooth muscle Cardiac muscle
Glands
Interneurons
• Connect neurons within the CNS – Sensory ‐ ‐> Sensory – Motor ‐ ‐ > Motor – Sensory ‐ ‐ > Motor
• Analysis of sensory inputs • Coordina8on of motor outputs • May be excitatory or inhibitory based on the effect on the postsynap8c membrane of other neurons
The Synapse
• Communica8on from a neuron to an effector • A nerve impulse triggers events that transfers informa8on
• Chemical – Vesicular synapse – Neurotransmiber released from presynap8c membrane
– Binds to receptors on postsynap8c membrane
• Electrical – Gap junc8ons
Anatomical Organiza8on of the Nervous System
Central Nervous System • Center • Nucleus
– Collec8on of nerve cell bodies • Neural cortex
– Superficial gray maber
• Tracts – White maber
• Columns • Pathways
– Ascending (sensory) – Descending (motor)
Peripheral Nervous System • Ganglia
– Collec8on of nerve cell bodies – Gray maber
• Spinal nerves – White maber – Emerge from the spinal cord – All mixed nerves
• Cranial nerves – White maber – Emerge from the brain – Sensory – Motor – mixed